Alpha, beta and gamma radiation

STARTER ACTIVITY:

* List some Greek symbols and their meanings:

greek symbols meanings Alpha beta gamma

Pi theta delta omega

summation ohm wavelength

Lesson objectives; You will learn:1. The nature of alpha beta and gamma2. The properties of alpha beta and gamma3. Why these radiations are dangerous

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Alpha, beta and gamma radiation

Types of radiation

1) Alpha () – a nucleus decays into a new nucleus and emits an alpha particle (2 protons and 2 neutrons – the nucleus of a helium atom)

2) Beta () – a nucleus decays into a new nucleus by changing a neutron into a proton and electron. The fast moving, high energy electron is called a beta particle.

3) Gamma – after or decay surplus energy is sometimes emitted. This is called gamma radiation and has a very high frequency with short wavelength. The nucleus is not changed.

Unstable nucleus

Unstable nucleus

Unstable nucleus

New nucleus

New nucleus

New nucleus

Alpha particle

Beta particle

Gamma radiation

Alpha, beta and gamma radiation

Alpha, beta and gamma radiation

Q1.Why do Alpha and beta

deflect in opposite directions?

Alpha, beta and gamma radiation

Q2.Why does gamma not

deflect in a magnetic field?

Alpha, beta and gamma radiation

Ionization

An ion is a charged particle. Alpha , beta and gamma radiations have the ability to ionize atoms when they collide with them. The charged particles that are created are potentially very dangerous - particularly if they belong to your body!

This is the symbol for radioactive materials

+-

How does ionization happen?

An Atom Nucleus (positively charged)

An electron (negatively charged)

Atoms are neutral as they have equal numbers of positive and negative charges

+-

How does ionization happen?

An Atom

+

The charged particle left behind is called an ion. We say that the atom has been ionized.

Ionisation

When radiation collides with neutral atoms or molecules it alters their structure by knocking off electrons. This will leave behind IONS – this is called IONISING RADIATION.

particle

Electron

+

Why are ionizing radiations dangerous?

If they ionize atoms in living cells they can cause the cells to mutate, and this can lead to cancer.

Each time an atom is ionized the radiation particle loses energy. They slow down and eventually stop. At this point they are harmless as they can do no more damage.

Alpha particles are strongly ionizing. They produce many hundreds of ions per cm when they travel through air. But this means they lose their energy quickly and stop after a few cm.

Alpha source

Where would these be most dangerous?

Thin paper

Beta particles are less ionizing. They lose their energy more slowly and can travel much further in air than alpha particles.

beta source

Does this make beta particles less dangerous?

Thin paper

Aluminium sheet

Gamma rays are not very ionizing. They travel unimpeded through air. In fact, you need several cm of lead or concrete to reduce their level, but even then, a lot still get through.

gamma source

Does this make them less dangerous than alphas and betas?

Thick lead

Alpha, beta and gamma radiation